2. Weapon SkinsThere are three types of weapon skins in Counter Strike:
p model--> the model seen in third person view while a player holding it
v model--> the model seen in first person view
w model--> the model seen in third person view while scattered on the map
The file name formats are:
p_*weapon name*.mdl, v_*weapon name*.mdl, and w_*weapon name*.mdl
Valid weapon name refers to all weapons in Counter Strike, such as ak47, aug, p90, etc.

Just like installing the Character skins, you just have to put the *.mdl file in cstrike/models folder.
Backup your default skins first just in case something went wrong.